1. Field of the Invention:
The present invention relates to a polishing apparatus for polishing a workpiece such as a semiconductor wafer to a flat mirror finish, and more particularly to a polishing apparatus having a rotary transporter for supplying workpieces to a polishing position.
2. Description of the Related Art:
In semiconductor device manufacturing processes, semiconductor wafers are polished to a flat mirror finish in a semiconductor wafer fabrication process, and layers formed on semiconductor devices are polished to a flat mirror finish in a semiconductor device fabrication process. These polishing processes in the semiconductor wafer fabrication process and the semiconductor device fabrication process are performed by a polishing apparatus, called a chemical mechanical polishing apparatus.
Conventionally, such a polishing apparatus has been designed as a dedicated polishing apparatus having a single function of polishing semiconductor wafers. The semiconductor wafers which have been polished by the polishing apparatus are transported to a next cleaning process by a movable water tank containing water in which they are immersed to keep them from drying during transportation. However, this separated polishing and cleaning process tends to impair the cleanliness of a clean room, and the polished semiconductor wafers need to be transported by an operator or a manually operated transportation means. Further, a large installation space is required for two kinds of apparatuses comprising a polishing apparatus and a cleaning apparatus that is used to carry out the subsequent cleaning process.
In an effort to make the polishing process clean and reduce the installation space of the apparatus, there has been developed a polishing apparatus which performs both a polishing process and a cleaning process and which is of a dry-in and dry-out type for introducing semiconductor wafers therein in a dry condition and removing polished and cleaned semiconductor wafers therefrom in a dry condition.
On the other hand, the polishing apparatus having a single function of polishing semiconductor wafers has been improved to allow the cleanliness of a clean room to be maintained, and the polishing apparatus and the cleaning apparatus used in a cleaning process after polishing have an increased processing capability for thereby reducing the number of the polishing apparatuses used for polishing processes and the number of the cleaning apparatuses. As a result, the conventional dedicated polishing apparatus having a single function of polishing semiconductor wafers can reduce an installation space thereof to a degree which is equal to or smaller than the dry-in and dry-out type polishing apparatus.
However, in the dedicated polishing apparatus having a single function of polishing semiconductor wafers, the semiconductor wafers which have been polished by the polishing apparatus are transported still by an operator or a manually operated transportation means, as before. If the transportation means is automated, then it is difficult to handle the semiconductor wafers because the semiconductor wafers are stored in the movable water tank. Thus, the problems are presented by the transportation means in the conventional dedicated polishing apparatus.
Further, the dry-in and dry-out type polishing apparatus has a processing capability per unit time and unit installation area lower than the conventional dedicated polishing apparatus. Thus, the number of apparatuses in the polishing processes is large, a large installation space is required, and the running cost of the apparatuses is high.
It is therefore an object of the present invention to provide a polishing apparatus which can be used as a dry-in and dry-out type polishing apparatus, and has a high processing capability per unit time and unit installation area for processing workpieces such as semiconductor wafers.
Another object of the present invention is to provide a polishing apparatus which can reduce or minimize the number of times of transfer of a workpiece such as a semiconductor wafer while the workpiece is transported from a reversing device to a top ring.
According to the present invention, there is provided a polishing apparatus comprising: a turntable having a polishing surface; a top ring for holding a workpiece and pressing the workpiece against the polishing surface to polish the workpiece; a rotary transporter disposed in a position which can be accessed by the top ring and having a plurality of stages positioned on a predetermined circumference from a center of rotation of the rotary transporter; a plurality of support tables removably held by the respective stages of the rotary transporter for supporting workpieces respectively; and a pusher for vertically moving the support table and transferring the workpiece between the support table and the top ring.
According to the present invention, it is possible to shorten the time required to transfer a workpiece to be polished, such as a semiconductor wafer, to the top ring, thereby greatly increasing the number of processed workpieces per unit time, i.e. throughput.
In a preferred embodiment, the polishing apparatus further comprises a reversing device for reversing the workpiece; and a lifter for vertically moving the support table and transferring the workpiece between the support table and the reversing device.
Thus, the transfer of a semiconductor wafer as a workpiece to be polished from the reversing device to the top ring can be performed by the wafer support tables removably held by the respective stages of the rotary transporter. Thus, for example, the transfer of the semiconductor wafer between the lifter and the rotary transporter or between the rotary transporter and the pusher may be eliminated to prevent dust from being generated and prevent the semiconductor wafer from being damaged due to transfer error or clamping error.
In a preferred embodiment, a plurality of the support tables comprise a loading support table for holding the workpiece to be polished and an unloading support table for holding the workpiece which has been polished.
With the above arrangement, the semiconductor wafer to be polished is transferred not from the pusher but from the loading wafer support table to the top ring, and the polished semiconductor wafer is transferred from the top ring not to the pusher but to the unloading wafer support table. Thus, the loading of the semiconductor wafer to the top ring, and the unloading of the semiconductor wafer from the top ring are conducted by respective jigs (or components), i.e. the support table, and hence the abrasive liquid or the like attached to the polished semiconductor wafer is prevented from being attached to a common support member for performing loading and unloading of the semiconductor wafer. As a result, the solidified abrasive liquid or the like is not attached to the semiconductor wafer to be polished, and does not cause damage to the semiconductor wafer to be polished.
In a preferred embodiment, the rotary transporter comprises a plurality of guide blocks provided circumferentially at certain intervals on each of the stages for removably holding the support table.
In a preferred embodiment, the guide block has at least one of an inner surface which has a tapered surface for centering action and an outer surface which has a tapered surface for centering action.
With the above arrangement, centering of the support table with respect to the guide blocks can be performed by the tapered surface.
In a preferred embodiment, each of the top rings is angularly movable about a rotating shaft to a position over one of the turntables and a position over one of the stages of the rotary transporter.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.